302 GEOLOGY OF A PORTION OF SHELBURNE CO., 



belonging to this granitic intrusion. The quartzite is highly 

 contorted and the mica is a phase of the exomorphic metamor- 

 phism. 



In a hand specimen the rock is seen to be a pinkish, very 

 fine-grained granite, minutely porphyritic. The feldspar 

 shows albite twinning in the larger crystals. Mica is dis- 

 tributed unevenly through the rock in small quantities, both 

 muscovite and biotite being present. The quartz lies between 

 the feldspar and is less conspicuous. In thin section the rock 

 is seen to consist of feldspar in hypidiomorphic crystals, a 

 much smaller amount of quartz, rather abundant secondary 

 muscovite, an occasional biotite flake, and some chlorite and 

 titanite. The feldspar is largely a microcline microperthite 

 with smaller amounts of oligoclase. The centers of many 

 :>f the feldspar crystals are filled with specks of sericite. 



The quartz diorite appears to form the remainder of the 

 igneous rock of the area. Outcrops were noted a half mile 

 west of Barrington, at Harrington Passage and to the south- 

 ward in railroad cuts, and at Shag Harbor. It is a light grey, 

 fine grained rock and shows the effect of shearing, the biotite 

 flakes being orientated into parallelism. Albite-twinned white 

 feldspar and colorless quartz in small amount may be seen 

 in the rock. The grain of the rock is fine, but a few feldspar 

 phenocrysts one-half inch in length may be seen. Under the 

 microscope the constituents are found to be hypidiomorphic 

 crystals of feldspar, a small amount of brecciated quartz 

 showing undulating extinctions, large plates of biotite often 

 clustered in the more brecciated places, accessory titanite 

 in small granular aggregations, quite numerous long rods of 

 apatite occurring in association with the biotite, and a very 

 small amount of iron ore, zircon and muscovite. The feldspar 

 is principally oligoclase twinned after the albite and pericline 

 laws, with smaller amounts of microcline microperthite and 

 albite-oligoclase. The more acid feldspars do not appear in 



